Submerged friction stir processing of AZ31 Magnesium alloy

Friction stir processing (FSP) has recently emerged as a microstructural modification technique. FSP can be used to effectively produce ultrafine and homogenous grain structure. The process is found to be very sensitive to thermal histories. Peak temperature, heating and cooling rate play a crucial role in controlling the resulting grain structure and consequently the mechanical properties of the processed material. In this work, AZ31 Magnesium samples were friction stir processed while sub-merged in room-temperature and warm water. For comparison, FSP in air medium was also performed. The effects of submerging conditions on thermal fields, power consumption, resulting grain structure and tensile properties were discussed in this work.

► Submerged friction stir processing has been proven to give more grain refinement for Mg AZ31 alloy.
► Resulting grain structure and tensile properties are very sensitive to thermal boundaries in FSP.
► Formability of Mg AZ31 at room temperature significantly enhanced by FSP (up to nine times when submerging with hot water).